Telephone-exchange system.



' Patented Dec. 4, I900. A. STRD'MBERG.

TELEPHONE EXGHANGE SYSTEM.

(Application filed Oct. 18, 1899.)

(No Model.)

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VNITED STATES PATENT OFFICE.

ALFRED STROMBERG, OF CHICAGO, ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

sPEcIFIoA'rioti forming part of Letters Patent No. 662,984, dated December 4, 1900.

Application filed October 18, 1899. Serial No. 733,959. (No model.)

T0 on whom it may concern:

Be it known that I, ALFRED STROMBERG, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone -Exchange Systems, (Case No. 1,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming apart of this specification. My invention relates to telephone-exchange systems, and more particularly to that class of telephone-exchange systems in which common batteries are employed, and has for its object the provision of means for reducing the number of cord-strands employed in connecting subscribers for conversation.

I am enabled by means of my invention to connect two metallic-circuit telephone-lines together in a telephonic circuit by a single cord-strand and to connect a common battery with the telephone-lines for the purpose of operating signals and for supplying transmitters at the subscribers stations with current from the said battery.

Generally speaking, the preferred embodiment of my invention consists in a plurality of metallic circuit telephone lines having transmitters at the substations,a common battery at the exchange, one limb of each telephone-line being permanently connected with one terminal of the battery, a line-jack connected with each ofthe remaining limbs of the metallic circuits, and a cord and plug connecting apparatus employing a single cordstrand and preferably two connecting-plugs, the line-connectin g apparatus at the exchange being so arranged that one side of the united telephonic circuit between subscribers stations is completed solely by the agency of the single cord-strand, while the other side of the metallic circuit is completed by the two limbs of the subscribers lines permanently connected with the battery. When subscribers are connected for conversation, the battery is connectedin parallel between the limbs of the united telephone-circuit, that terminal of the common battery Which is not permanently connected with limbs of the metallic telephone-line being preferably permanently connected with the single cord-strand. I preferably also provide means whereby the apparatus used in connecting metallic-circuit telephone-lines equipped in accordance with my present invention may also be employed for uniting an ordinary metallic telephone-line with a telephone-line of my improved system. To this end I preferably employ a doublecontact plug, an extra cord-strand leading from that terminal of the battery permanently united with limbs of the metalliccircuit lines to the extra contact upon the double-contact connecting-plug.

I will explain my invention more particularly by reference to the accompanying drawing, which diagrammatically illustrates a telephone-exchange system equipped in accordance with my invention.

The apparatus at the substations 10 and 90 is well known to those skilled in the art. A battery-transmitter ct, with its coil 17 and the receiver 0, is illustrated at each of these stations, a secondary coil at each station in this particular instance being included in a local or short circuit with the telephone-receiver 'thereat, while the primary coil in circuit with the transmitter is placed in circuit with both limbs of the corresponding telephone line upon removal of the receiver from its spring switch-hook. The transmitter primary winding of the induction-coil at station 10 is thus shown in series with the telephone-line, the telephone-receiver at this station being removed from its hook. The transmitter-circuit at station 90 is open, the receiver at said station being upon its hook. I do not, however, Wish to be limited to the precise arrange ment of the telephone apparatus at the subscribers stations that I have shown. There is also provided at each station a call-bell d, preferably responsive to alternating current in bridge with a condenser of the corresponding telephone-line. Other connections for the call-bells, however, may be employed. The metallic-circuit telephone-lines extend from the substations to the exchange. One limb e of each metallic line is connected with line-jacks f and g at sections 1 and 2' of the multiple switchboard and also with an answering-jack h at section 2. The remaining limbs 11 of the metallic lines are connected with one terminal of the common battery 70.

ed with the remaining terminal of the common battery that is not permanently connectf ed with the limbs 1).

A subscriber when initiating a call by removing his receiver from its switch hook completes a circuit which includes the common battery and his line-indicator. In response to the line-signal the operator inserts an answering-plug it within the answeringjack of the calling subscriber-say No. 10- and thereby opens the circuit through the indicator 'm to cause its restoration.

I provide an operatofis telephone and ringing-key Z in connection with each cord set.

By operating the key the operator may include her telephone in telephonic communication with the calling subscriber or with connected subscribers. Calling subscriber No. 10 desiring connection, for example, with called subscriber No. 90 inserts the connecting-plug 7" within the line-jack g of the called subscriber. The operator by operating her key Z may signal the called subscriber. It will be observed that although the connecting-plug r is provided with a tip and a sleeve the sleeve alone is connected with the cordstrand 0, the tip-strand of the connectingplug being disconnected when subscribers whose lines are both equipped in accordance with my present invention are connected for conversation. I thus am enabled to connect two metallic-circuit telephone-lines together for conversation through the agency of a single cord conductor and am enabled to employ .a common battery which serves the purposes for which common batteries are now employednamely, for the operation of the signals and to supplythe transmitter-circuits with current.

I include a clearing-out indicator t perma nently between the cord-strand 0 and that terminal of the battery 7c connected with the limbs c. This indicator is energized while either or both of the telepl'ione-receivers at the substations are off their hooks. When the subscribers are through conversation, the circuit including the clearing-out indicator and the battery is broken by means of the condensers at the substations, whereby the clearing-out indicator is restored, signifying tothe operator that conversation between the subscribers is finished.

I have shown an additional station A, which employs a magneto-generator u at the substation for the purpose of operating the lineindicator 0 at the exchange. The substation A in this instance may be provided with a magneto-transmitter or a battery-transmitter. The telephone-line leading to this substation is metallic. If the calling subscriber should wish telephonic connection with subscriber A, the connecting-plug r wi ll serve to complete the telephonic connection, the tipstrand connected with the limbs '21 serving to complete the telephonic circuit between the calling subscriber N0. 10 and the called subscriber A, the tip engaging the shorter linespring of the spring-jack corresponding to subscriber A, the longer line-spring being engaged by the sleeve of the connecting-plug.

I do not wish to be limited to the employment of the exact apparatus shown; but,

Having thus described my invention, I claim as new and desire to secure by Letters Patent-e 1. In a telephone-exchange system,the combination with a plurality of metallic-circuit telephone-lines each extending by both of its limbs from a subscribers station to an exchange, limbs of the metallic telephone-lines being directly connected together at the exchange, independently of cord connecting apparatus, of a single cord strand provided with suitable connecting means adapted to connect the remaining limbs of the metalliccircuit telephone-lines, the telephonic circuit between the subscribers thereby comprising the limbs of the metallic lines that are directly connected at the exchange and the single cord -strand with the remaining limbs united thereby, battery-transmitters being provided at the substations, a common battery for supplying said transmitters connected in bridge at the exchange between the cordstrand and the directly-united limbs of the telephone-lines, the directly-united limbs of the telephone-lines being free of direct connection except atthe exchange where they are directly connected with one terminal of the battery, and an indicator in the same bridge with the battery, substantially as described.

2. In atelephone-exchange system,the combination with a plurality of metallic-circuit telephone-lines each extending by both of its limbs from a subscribers station to an exchange, limbs of the metallic telephone-lines being directly connected together at the exchange, independently of cord connecting apparatus,of a single cord-strand provided with suitable connecting means adapted to connect the remaining limbs of the metallic-circuit telephone-lines, the telephonic circuit between the subscribers. thereby comprising the limbs of the metallic lines that are directly connected at the exchange and the single cord -strand with the remaining limbs united thereby, battery-transmitters being.

provided at the substations, a battery for supplying said transmitters having one terminal connected to those terminals of the limbs of the telephone-lines that are directly united, the directly-united limbs of the telephonelines being free of direct connection except at the exchange where they are directly connected with one terminal of the battery, the remaining terminal of the battery being directly connected with the cord-strand, and a clearing-outindic'atorincluded in circuit with the said battery, the said clearing-out drop and battery being in a bridge of the united telephone-lines, substantially as described.

3. In a telephone-exchange system,the combination with a plurality of metallic-circuit telephone-lines each extending by both of its limbs from a subscribers station to an exexchange and the single cord-strand with the remaining limbs united thereby, the connecting means employed with the cord comprising in part a connecting-plug having two contacts, one of which is connected with the said 25 cord-strand, while the other is connected by an additional cord-strand with the directlyunited terminals of the telephone-lines whereby the said additional telephone-line may be united in telephonic circuit with metallic-cir- 3o cuit telephone-lines that have directly-connected limbs, substantially as described.

In witness whereof I hereunto subscribe my name this 16th day of October, A. D. 1899.

ALFRED STROMBERG;

Witnesses:

GEORGE L. GRAGG, C. E. HUBERT. 

